Help with some y9 maths?

Have you ever heard the saying Ďthere are more Collingwood supporters than there are grains of sand on Earthí?

Well just how many grains of sand are on Earth? Letís do some rough calculations. We will define a grain of sand as unconsolidated (so no sandstone) and we will only look at sand residing at or near the surface. If we do that we find that these regions comprise about 30% of the surface of the Earth. If we take those numbers and then multiply them by the surface area of the planet we have the area that contains sand. If we assume an average depth for sand in these regions is 10m we can thus calculate volume. All we need now is the volume of a sand grain and we can calculate the number of grains needed to fill that volume. Grains of sand range in diameter from ~1mm to 0.0625mm. A simple result would just divide the two volumes, but this would ignore how the grains are packed (how much void space exists). The void space could range from a few to fifty percent. Doing all of this I find that the number of grains of sand on Earth is approximately 2.0 x 1023.So no, there are more Collingwood supporters!!

If one were to cover the 6 states and 2 territories of Australia with the same number of M&Mís as there were grains of sand, what would the thickness of the layer of M&Mís be closest to? To help you answer this difficult question, answer the following:

A 100 mL measuring cylinder holds how many M&Mís? 90

Work out the volume of 1 M&M (in cm3). 100 / 90 = 1.111cm^3

Work out the volume of the same number of M&Mís as there are grains of sand.

Convert this volume to m3.

Find the area of Australia in km2 (with your answer you must write down your source). 7,692,024 km^2

Convert this to m2. 7,692,024,000,000m^2

Calculate the depth to which Australia would be covered by M&Mís.

This is my assignment and i've answered a few questions but have no idea what the others mean or what i'm meant to do, any pointers or help appreciated, thanks!